In certain vehicle suspension systems for mounting the frame or beds of the vehicle on wheels, it is common practice to provide a load-bearing axial support secured to the vehicle and to provide a yieldable connection between this centrally-located support and the suspension system. Most commonly, the suspension system comprises one or more sets of leaf-spring members which pivot about the load-bearing support and whose extremities terminate at the wheel axles. In fact, the prior art has recognized certain advantages in providing for such pivotal motion. For example, U.S. Pat. No. 3,018,143 discloses and claims a bearing construction for a vehicle suspension which permits relatively free movement of the suspension system around the centrally-located load-bearing axle. A similar disclosure is made in U.S. Pat. No. 2,481,891, which teaches the use of a yieldable bushing member, such as rubber, compressed about the load-bearing shaft.
It has now been found, however, that pivotal movement about the centrally located load bearing axial support can have devastating effects upon the roadway upon which the vehicle travels. Semi-tractor trailer rigs are designed to carry impressive loads which are obviously supported by the rig's wheel axles and suspension systems. It has been found that the pivoting action which at one time was thought to be so desirable actually causes the axle-suspension assembly to bounce upon the roadway surface due to surface undulations which cause the wheel axle members to pivot about the centrally-located load-bearing axle. This bouncing effect is not only uncomfortable to the driver and possible harmful to the load being carried by the semi-tractor trailer rig, it also causes the entire weight of the rig to concentrate itself upon one wheel axle and then another, which in turn acts to break up a roadway's surface and significantly reduce its projected life.
It is thus an object of the present invention to provide a vehicle suspension system which includes a centrally-located load-bearing axial support which resists pivotal movement by the wheel axle members across said support.
It is yet a further object of the present invention to provide a method of converting currently-available and used vehicle suspension systems which include a load-bearing centrally-located axial support to a suspension system in which the wheel axles do not significantly pivot about said support.